Known printing techniques require various ink formulations. Such techniques include, for example, digital printing, laser printing, electro-ink printing, electro-photographic printing, displays and ink jet printing. Since the mid-1980s Color Electro-photographic (EP) Printing commonly known as laser printing technology, has been a popular choice with businesses and personal users who demand high quality, professional looking printed communications. With EP currently in its third generation of significant improvements, segment leaders are making key advancements in system design and supplies refinement and improvement.
With any printing technique utilizing an ink that comprises particles, it is important that the particles remain dispersed in the ink medium for extended periods of time. Significant sedimentation can result in poor print quality in any of the above techniques. For example, electro-photographic printing or laser printing requires ink compositions having high dispersion of the particulate pigments in the ink composition. In addition, it is important that the ink composition exhibit low conductivity.
One method for reducing sedimentation in ink compositions involves the addition of dispersants to the ink composition. Three major categories of dispersants are ionic (anionic and cationic), non-ionic and amphoteric. Stabilization of ink dispersions may be achieved with ionic dispersants, but the dispersants give rise to highly charged compositions that are not suitable for at least some types of printing that require minimal or no charge.